U.S. Pat. Nos. 4,341,294 and 5,638,931 disclose overrunning couplings that include inner and outer races, the inner race being split to provide a variable internal diameter, and multiple rollers situated between the inner and outer races. The rollers register with internal spiral surfaces formed in the outer race and external spiral surfaces formed in the inner race. The spiral surfaces are engaged by the rollers to effect a locking action of the clutch. This develops a radial force on the inner race, causing the inner race to engage a torque transfer shaft that is surrounded by the inner race.
Copending patent application, Ser. No. 09/228,129, filed Jan. 11, 1999, entitled "MULTIPLE FUNCTION CONTROLLABLE OVERRUNNING COUPLING", discloses a hydrostatic pressure actuator for triggering the engagement and release of the rollers. That copending patent application is assigned to the assignee of the present invention.
U.S. Pat. No. 5,305,663, issued to Allan S. Leonard et al, discloses a compound planetary gear transmission for use in an automotive vehicle and driveline wherein friction clutches and brakes are used to control the motion of the elements of the gearing to effect ratio changes. Engagement and release of the friction clutches and brakes of the transmission require precise control of the timing of the engagement and release in order to effect a smooth transition from one ratio to the other.
The control system disclosed in the '663 patent responds to driveline variables so that the shift event occurs rapidly with a smooth transition. The control system accommodates varying torque levels and changes in direction of the torque delivery through the gearing. The friction elements are controlled by fluid pressure-operated servos and clutch actuators, the actuating pressure being modulated to minimize the effects of inertia torque as the elements of the gearing change speed during a shift event.